The Apparatus Architect Part 22-Designing Ladder Company Apparatus In the last installment of the Apparatus Architect we reviewed some of the considerations for designing adequate compartment space into the body of your ladder company apparatus, in order to carry the equipment and ground ladders that would be needed to meet the needs of your response area. Having this knowledge of exactly what equipment is used most frequently and what particular length ground ladders are used on the fire ground will help the apparatus committee in working through these important issues when developing the specifications for your new aerial unit. As we complete our discussions on ladder company apparatus we will review some of the inherent advantages of each type of aerial device and whether the aerial is midship or rear mounted. If your department is in the process of replacing an existing aerial device it would be a great idea to break out a tape measure and record the wheelbase, overall length and overall height of the present rig. This will provide the committee with a barometer of the critical measurements when evaluating new vehicles. Any fire department buying a new aerial apparatus should measure the available clearance through the overhead door and the useable depth in the apparatus bay where the rig will be stored. More than one fire department has been surprised when they took delivery of their new 100 foot rear mount tower ladder, only to find out that the rig didn t fit into the station because it was too high. Don t take the word of another member in the fire company about how big the bay is, actually measure the door opening and if needed, place the ladder truck into the door opening to determine the exact clearance that you have in the apparatus bay. The maximum allowable dimensions for the 1
apparatus must be clearly spelled out in your specifications in order to allow prospective bidders to prepare an adequate bid response. Completing the Apparatus Purchasing Specification Form in Annex B of the NFPA 1901 standard would be a good start for any apparatus committee to undertake prior to setting out with the specification process. First, lets look at midship mounted aerial devices and what design features they offer. A midship aerial device provides a lower overall travel height for those departments that have reduced height bay doors, bridges or underpasses that would restrict travel. By varying the position of the turntable on the chassis frame, the overall travel height of the apparatus can be modified to meet the individual needs of the fire department. As the overall height of the vehicle gets lower the space for ground ladder storage and the useable compartment space is reduced accordingly. The NPFA requirement for enclosed compartment space on an aerial ladder or quint is forty cubic feet with a payload capacity of 2500 pounds. Unfortunately, many ladder trucks are designed to meet these minimum standards but have little or no useable space to accommodate the needed equipment and ground ladder compliment. Midship aerial devices are generally easier to spot and position on the fire ground as the center mounted turntable allows the operator to locate the center of the turntable with the midpoint of the structure. Units which have raised roof cabs can inhibit the ability of the aerial device to operate at low angles when the device is working off the front of the apparatus. This is particularly important with mid-mounted tower ladders where it may be impossible to operate the tower at angles below thirty to thirty five degrees. While many manufacturers offer reverse slope rear walls on the cab and collision avoidance systems for the device, it is best to actually operate an identical unit at the critical 2
buildings in your first due area to insure that what you want to purchase will actually work for you. Do not let the apparatus salesmen bring in the latest and greatest aerial apparatus, set in up in the biggest parking lot in town and tell you that your department has to have it. When was the last time you responded to a parking lot on fire? The apparatus must be taken to the down town area and you as the consumer must insist that the salesman puts the apparatus through it paces. How many aerial apparatus demonstrations take place and the salesmen never flow s water? Too many to even count. Also Raised Cab Roofs on mid-mounted Tower Ladders should be avoided if at all possible as it will cut down the operational effectiveness of the apparatus. Your fire department may be limited to a midship aerial design due to overall height limitations within the community and if so, then the committee should work diligently to develop specifications that provides the maximum number of components that will benefit the department. Midship aerial and tower ladder devices offer superior scrub area coverage on buildings when compared to rear mounted apparatus. Scrub area being defined as that part of the tower ladder bucket or the tip of the aerial device that can touch the building line. The better the scrub area of a particular aerial device the more use your department will get on the fire ground. Better scrub area is a direct result of apparatus positioning on the fire ground, apparatus design and what vendor you choose to build your aerial device. Design features such as outrigger placement, body heights and ground ladder arrangement are much more user friendly than rear mounted devices and with the assistance of an Apparatus Architect the fire department can often benefit from there input and perspective. The discussion of rear mounted aerial devices needs to be broken down between aerial ladders versus aerial towers. These units generally produce a higher overall height vehicle, however with the 3
use of low profile cabs these units can sometimes still fit into an eleven foot bay door. Rear mount aerial ladder trucks can be built on short wheelbase chassis to make the unit more maneuverable in tight locations. For a given specified overall height, the body configuration on a rear mount unit can offer the department more options with respect to compartment dimensions and ground ladder storage. These ladders can be mounted both within the body and carried in a side stack arrangement, in addition to carrying a roof ladder within the fly section of the aerial device. Where the NFPA 1901 standard only calls for five ladders totaling 115 feet, rear mount aerial ladder units can be effectively designed to carry upwards of 250 feet of ground ladders in various configurations. Purchasing a rear-mounted aerial ladder could prove to be a big benefit for your department. Rear mounted aerial tower units have become the unit de jour in many departments. Those departments that were not restricted by the size of the apparatus bay or other hazards rapidly acquired these types of devices as they were the largest and tallest rigs available. While this type of aerial tower offered good vertical and horizontal reach, the effective scrub area is limited by the design of the turntable and height from the ground, together with the elevation limits of the hydraulic cylinders. The angle of departure off the side of the apparatus is much greater for a rear-mounted tower ladder vs. a mid-mounted tower ladder; this cuts the scrub area of the rear-mounted tower ladder significantly. If your department has not previously operated a rear mount aerial tower consider that a significant amount of driver and operator training will be required prior to placing the unit in service as the physical size of the vehicle and the front overhand of the platform may necessitate some changes in response patterns and procedures. The outrigger stance for these devices are generally wider than other types of aerial equipment and this also must be considered when 4
planning for the deployment of these rigs in tight situations. Given everything else being equal there are far more advantages in choosing a mid-mounted tower ladder over a rear mounted tower ladder. On several occasions we have been asked to present an overview of the different types of aerial ladder and tower devices to department apparatus committees prior to starting the formal specification process. Without reservation, many departments which do not currently operate any type of ladder company apparatus have convinced themselves that they need a 100 foot tower quint with a 500 gallon water tank, foam system and a full compliment of hose. The prevailing wisdom appears to be that if you bring a little bit of everything to the fire you can never be caught short! It is almost as if the apparatus committee is afraid or intimidated. Why did you buy that 100 foot ladder? It is the longest tower ladder offered and no one can ever accuse the apparatus committee of buying a ladder that came up short on the fire ground. Why did the apparatus committee put a bucket on the end of the ladder? So that no one could ever accuse the apparatus committee of providing a rig were someone might fall off the ladder, they can now ride in the bucket. In fact many firefighters have told us that the reason they bought a tower ladder instead of an aerial ladder is that everyone would rather ride in the bucket rather than climb the ladder. Riding in the bucket has never been a good reason to expend an additional $100,000.00 in taxpayer money. Although both a bucket and a 100 foot reach are nice to have on an aerial device they simply may not be needed. In the past six articles in the Apparatus Architect series we have taken you through some of the questions, concepts, considerations and pitfalls that your apparatus committee should evaluate during the purchasing process for your new ladder company unit. It is important to remember that decisions 5
that you make at this point will impact the department training and operations for many years to come. Remember the slogan: An educated consumer is our best customer. Work towards designing a practical, useful and most importantly safe ladder truck and lets make sure that Everybody goes home after the run. When in doubt, get outside help, hire an apparatus architect. In the next installment of the Apparatus Architect we will begin our discussion on special service units and how they can compliment our operations at accident and fire ground scenes. CAPTIONS FOR PHOTOS-APPARTUS ARCHITECT PART 22 Slide #1: The Levittown, New York Fire Department operates this well designed Pierce Lance 105 foot rear mount aerial ladder. Ladder 626 carries an extensive compliment of ground ladders on the right side of the body as well as off the rear of the truck. Digital image by Tom W. Shand Slide #2: Tower 244 operated by the Oceanside, New York Fire Department shows the size and available compartment space that can be acquired on a non-quint aerial tower. Note the overhang of the platform basket over the windshield. This 6
department also operates a Pierce rear mount aerial ladder to compliment their apparatus fleet. Digital image by Tom W. Shand Slide #3: The Peoria, Arizona Fire Department operates this American LaFrance mid-mount tower ladder as Ladder 193. Note the height of the side body compartments and the lack of any equipment on top of the body that could inhibit use of the tower at low angles. Digital image by Tom W. Shand Firehouse Magazine February 2005 By Tom Shand and Michael Wilbur 7